I use Windows Defender on my notebook computer, and it often updates very slowly. I think it's just Windows servers. Sometimes Windows updates themselves seem to take forever, even though they should be going a lot faster. It took over an hour for the Windows updates to download for me tonight, and they were less than 400MB, yet my actual Hughesnet speed is very good and the updates should have been over in less than five minutes.
As for ITunes, it seems to be a problem for a few people.